In U.S. Pat. No. 5,020,091 there is described a cellular telephone communications system that includes multiple cells covering a geographical area, such as a metropolitan area. To the base station of each cell a number of frequencies are assigned, with some of the assigned frequencies being specified as control channels used for reciprocal identification between the telephones and the system. The location of the dedicated control channels in the cell's frequency spectrum identifies the type of cellular system, A or B (see, for example, EIA/TIA-553). A metropolitan area typically has one of each type of system.
In a cellular system of most interest to this invention the channel from a base station to the mobile station is referred to as the forward channel, i.e., the forward control channel and the forward voice channel. The channel from the mobile station to the base station is referred to as the reverse channel, i.e., the reverse control channel and the reverse voice channel.
Base stations can transmit various messages over the forward control channel including, by example, mobile station control messages, overhead messages (e.g., Overhead Message Trains (OMTs)), and control-filler messages. Mobile station control messages are transmitted by a base station when paging or sending orders to a mobile station (see, e.g., EIA/TIA-553 Sec. 3.6.2.2 and Sec. 3.6.2.3). Overhead Message Trains are frequently transmitted by base stations. The OMT includes a System Parameter Overhead Message (SPOM), and may also include one or more Global Action Overhead Messages (GAOMs). The SPOM always contains System Identification (SID) information. The SID is unique for each cellular system. The use of the SID enables the cellular phone to determine whether it is using its home system or whether it is roaming. According to current standards (e.g., EIA/TIA-553), the SPOM is transmitted every 800.+-.300 ms, and the GAOMs are transmitted on an as needed basis.
Also according to current standards (e.g., EIA/TIA-553-A), GAOMs can include a Rescan Global Action Message (RGAM), a Registration Increment Global Action Message (RIGAM), a Location Area Global Action Message (LAGAM), a New Access Channel Set Global Action Message (NACSGAM), an Overload Control Global Action Message (OCGAM), an Access Type Parameters Global Action Message (ATPGAM), and Access Attempt Parameters Global Action Message (AAPGAM), a Random Challenge A Global Action Message (RCAGAM), a Random Challenge B Global Action Message (RCBGAM), a Local Control 1 Message (LC1M), and a Local Control 2 Message (LC2M). Exemplary formats of these messages, as in accordance with EIA/TIA-553-A, are shown in FIGS. 5a-5k, respectively.
A base station transmits OMTs to a mobile station in order to, by example, support the mobile station when it is executing the Initialization Task (see, e.g., EIA/TIA-553 Sec. 3.6.1 and Sec. 2.6.1), control the mobile station while it is monitoring a control channel (see, e.g., EIA/TIA-553 Sec. 3.6.2.1), and to support system access by the mobile station (see, e.g., EIA/TIA-553 Sec. 3.6.3.1).
To support system access by the mobile station, the base station transmits various messages in the OMT over the forward control channel (see, e.g., EIA/TIA-553-A Sec. 3.6.3.1). A first message is the Digital Color Code (DCC) message, which, after being transmitted from the base station to the mobile station, is used by the mobile station to identify to the base station which base station transmitter the mobile station is receiving. A second message includes the Control Mobile Attenuation Code (CMAC), which is transmitted from the base station in a control-filler message if the mobile station needs to adjust its transmitter power level before accessing the system on a reverse control channel. A third message includes the Wait-For Overhead Message (WFOM), which specifies whether or not the mobile station must wait to receive an OMT before accessing the system on a reverse control channel. Another message includes the Overload Control (OLC) message, which is appended to the SPOM if the mobile station must not access the cellular system for originations on the reverse control channel. Another message includes the Access Attempts Parameters Message (AAPM), which is appended to the SPOM to indicate that default values must not be used for a number of seizure attempts or the limit on the number of busy occurrences for the mobile station accessing the reverse control channel. A further message is the Access Type Parameters Global Action Message (ATPGAM). The ATPGAM indicates whether or not the mobile station must check for an idle-to-busy status transition on the reverse control channel when accessing a system.
Although a base station can transmit various types of messages to a mobile station over the forward control channel, current standards (e.g., EIA/TIA-533, EIA/TIA-553-A, IS-91, IS-95, and IS-136) for the analog mode do not include protocols for enabling the base station to notify the mobile station of the air-interface protocol version (e.g., AMPS) and the core analog roaming protocol version supported by the base station. By example, as can be seen in view of FIGS. 5a-5k, none of the GAOMs of EIA/TIA-553-A include data fields which specify air-interface protocol or core analog roaming standard information. As a result, if the mobile station is not able to be notified of the air-interface protocol version and the core analog roaming standard supported by the base station, the mobile station may originate messages that are not capable of being processed by the base station.
Current standards (e.g., EIA/TIA-533, EIA/TIA-553-A, IS-91, IS-95, and IS-136) also do not include protocols for enabling the mobile station operating in the analog mode to notify the base station of the air-interface protocol version, the core analog roaming protocol version, and the capability features (e.g., Call Waiting, Calling Line Identification) supported/not supported by the mobile station. By example, according to current standards (e.g., EIA/TIA 553), the types of messages that may be transmitted by a mobile station over the reverse control channel can include a page response message, an origination message, an order confirmation message, and an order message. The messages may consist of the words shown in FIGS. 6a-6j. FIG. 6a shows data fields of an Abbreviated Address Word (Word A) , and FIG. 6b shows data fields of an Extended Address Word (Word B). FIG. 6c shows data fields of a Serial Number Word (Word C). FIG. 6d shows data fields of Second Word of the Called-Address (Word E), and FIG. 6e shows data fields of an Authentication Word (Word C). A Unique Challenge Order Confirmation Word (Word C) is shown in FIG. 6f, and a Base Station Challenge Word (Word C) is shown in FIG. 6g. FIG. 6h shows data fields of a First Word of the Called Address (Word D), and FIG. 6i shows data fields of a Third Word of the Called Address (Word F) Also, FIG. 6j shows data fields of a Fourth Word of the Called-Address (Word G). As can be appreciated, none of these words include data fields which indicate the version of the air-interface protocol version supported by the mobile station, the core analog roaming protocol version supported by the mobile station, or the capability features supported/not supported by the mobile station.
Being that capability feature information and air-interface/core analog roaming protocol version information cannot be provided from a mobile station to a base station operating in the analog mode in accordance with conventional standards, cellular systems cannot differentiate between mobile stations that can process certain messages and those that cannot process these messages. Also, certain information such as, for example, Calling Line/Number Identification can be delivered by the base station to the mobile station using specific protocols, such as, for example, the Alert with information protocol or the Extended Protocol Calling Line Identification protocol. Unfortunately, however, since current standards for the analog mode do not enable the mobile station to notify the base station of the capability features supported by the mobile station, the base station has no way of determining the correct protocol to use in order to deliver the Calling Line/Number Identification to the mobile station. If the base station transmits a message to the mobile station, and the mobile station does not have the capability of processing the message, undesirable consequences can result. For example, the mobile station may not execute the message and/or a call may not be delivered to a user.
As is depicted in FIG. 1, a typical cellular network is divided into a number of regions (e.g., SID1-SID5) each having contiguous radio cells (shown nominally as hexagons). One region or SID may also include one or more paging areas, each encompassing one or more radio cells.